Fluid flow in industrial machinery conduits are usually controlled by a manual control valve provided with an outwardly projecting lever handle. The fluid, e.g. hydraulic fluid, is fed to the machinery to power same. The handle is transversely mounted to the valve about a pivotal axle for rotation between an "open" position, usually parallel to and in direct register with the conduit, and a "closed" position, usually orthogonal to the conduit. In the handle closed position, the valve gate is positioned transverse to the lengthwise axis of the conduit, wherein fluid flow is positively prevented therethrough. In the handle open position, the valve gate is positioned axially of the conduit, wherein fluid flow thereabout is substantially unhampered.
During maintenance of the fluid-fed machinery, it is essential not only to close the valve, but also to make sure that the valve remain closed at all time. Indeed, maintenance crewmen of large industrial machines may become severely injured and eventually sustain permanent disabilities or even be killed, if the valve is accidentally opened during machine maintenance work downstream of that valve. It is thus critical that the worker's machine maintenance protocol includes as a first step the releasable installation of a valve lock onto the valve by a maintenance crewman, before work downstream of the valve begins.
A review of prior art discloses that such valve locks exist. Such valve locks are devised to deter an accidental opening of the valve, e.g. by a fellow worker in the plant not aware that maintenance is currently being made on the machinery. However, these known valve locks are not intended to prevent a criminal from tampering with the valve in view of intentionally inducing bodily harm to the maintenance crewmen. Accordingly, their hardness is relatively small.
Typical of such valve locks is the one disclosed in U.S. Pat. No. 5,003,797 issued Apr. 2, 1991 to the W. H. Brady Company. The Brady valve locking device including a main, rigid, single planar body 25 provided with an inner channel member 30, to be engaged by the valve handle 12. An integral diverging leg 26 depends from the main body 25 of the lock. In the closed position of the valve handle, upon engagement of handle 12 into channel 30, leg 26 comes to flatly abut tangentially against the valve body 15 (the latter is coaxial to the fluid conduit 11). As shown in FIG. 6 of the Brady patent, locking action is obtained by pivoting arm 31 toward valve lever 12 and by engaging a padlock shackle into one of the bores 34, so as to wedge flange 28 against conduit 11. Of course, such a locking device is limited to locking the valve handle 12 in a closed position only.
U.S. Pat. No. 4,498,320 issued in February 1985 to Conbraco industries, inc., discloses a valve handle locking device consisting of two parts. This valve lock can lock the valve handle in both its closed or open position. But, as clearly suggested in FIG. 3, each time the two part lock 34, 36 is to be installed to the handle lever 24, a nut 30 has to be removed and then reinserted onto the rotatable valve shaft 22 of handle lever 24. This is cumbersome.
Canadian Patent 1,041,315 issued in 1978 to the Whitey Research Tool company, also discloses a two part valve handle lock, which can lock the valve handle in both a closed position or an open position. Again, as in the Conbraco patent, in order to install the two parts 52, 54 of the locking device onto the handle 56, the nut 16 connecting the handle 56 to the valve axle 12 has to be removed and then reinstalled.